Runner for grinding curved-glass surfaces



Sept. 16. 1924. y l

A. F. JOHNSTON RUNNER FOR GRINDING CURVED GLASS SURFACES 2 Shoots-Sheet l Original Filed Deo. 13 1920 Sept. 16, 1924.

- A. F. JOHNSTON RUNNER FOR GRINDING cum/ED GLAss Suances originl Filed Dec. 13 2 suena-sham 2 R m m m ALERT F. JOHNSTON, 0F FORD CITY,

TE GLASS COMPANY, 0F F0 Application filed December 18, 19%, Serial Eo. til. genewe February 6, '1924.` l

T o, all wm t may concern:

Be it known hat I, Amaai* F. JoHNsroN, a citizen of the United States, residing at Ford City in the county of Armstro land State of ennsylvania, have invente `certain new and useful Improvements in Runners vi'or Grinding Curved-Glass Surfaces, of which the following is a specification.

vThe inventionrelates to grinding runners designed for' use ingrinding, smoothing or polishing curved surfaces such as the inner and outer surfaces of glass blanks for use `as parabolic 4mirrors. It hasfor its principal objects the provision of an improved runner which will adapt itself to the general curvature of the surface to be ground and produce a finished surface which' accurately follows the desired curvature; which applies yielding, substitutionally uniform pressure, throughout the working area of-contact between the runner and the glass; and which lis of cheap, simple construction and requires a minimum amount .of skill in use. Certain embodiments of the invention are, illustrated in the accompanying drawings, wherein:

Figure l is a vertical section showing the improved runner i in position of use for grinding a convex surface. Figure 2 is a plan view of the bottom of the runner. Figure 3'is an enlarged section through a art of the runner and the table upon lwhit-ii it is mounted. Figure 4 is a plan view of the top of the runner. i Figure 5 is -a partial vertical section throu h a runner modified in construction for grinding a` concave surface, and Figure 6 is al partial vertical section through the edge of the runner and table when the'A runner is employed, for po In itspreferred form the runner comi prises a disc of felt or other flexible material felt sheet free so that it can adapt itself to' Which is unsupported except in its central portion where the spindle is attached, the intent beingv to leave .the outer portion of the the contour ofthe surface being ground. The front face of the sheet or disc is provided with metal grinding members, preferably inthe form of screws or nails having their shanks embedded in the felt and having their heads exposed so as to,` act as elallnents. These grinding elements era are pr'e arranged around the periph-A ery of the dlsc, the central portion ofthe means.

'side and the center o disc notbeing rovidedwith` any grinding When the runner is used for polishing, the metal grinding elements are, -of l course, omitted, rou or other polishing materialbeing emp oyed as in ordinary polishing operations.

The-general movements of the runner are similar to those which have already been which is the reverse of the direction' of rotation ofthe table. The runner-itself is preferabl left free to rotate with respect to its s in e and its diameter ispreferably such t at it overlaps the edge of the table on one the rotation of the table on the other side. A

Figure 1.A illustrates in a somewhat diagrammatic form the application ofthe run- Der in 'grindin a convex surface. In this construction 1 1s the table carrying the glass bl 2 Yand rotated from-the shaft 3; 4 is a felt sheet constituting the full member of the runner' 5 is a metal plate by means of whichthelt shea is connected to its spindle; 6 is the spindle-.mounted upon the arm 7; Sis the shaft by means of which the arm 7 is rotated; and 9 is the bearing ifor the shaft 8, such bearing being carried adjustably in the ,frame comprisingfthe channel barslO. 'l

The plate. 5 has a universal connection with the spindle 6 as indicated at 11 so that the runner' can adjlist itself to the glass and .the arm 7 is adjustable transversely in the .fork 12 carried by the lowerend of the shaft 8 so that the runner can be adjusted radially as desired, an adjusting nut 13 serving to clamp' the arm 7 in any adjusting position.

The lower face of the runner is provided ding elements inthe form of the studs 14 screwed into the felt sheet e 3. `These studs are din 'elements comes v lil.

lll

ening coating of Without the line of the table so that the er row of grinding elements cuts through the center line vof the table. The central portion of the felt sheet a docs not touch the glass being `spaced away therefrom by the felt blocks 15, shown in Figure 2, such bloclrs being secured to the. face of sheet 4l by screws or nails. The plate 5 is secured to the felt sheet by means of the bolts 16. "lhe felt blocks 1-5 prevent the bolt heads from touching the glass.

p ln order to provide for the necessary pres sure to give a proper gring action,a plurality of Wei lits 17, preferably arrange i as indicated in igure 4: are eniployd.. These weights are separated and independent so as to permit the felt sheet to adjust itself to the glass and various arrangements of -these Weights mi lit be made dependin i9 upon conditions. xperience has indicate however, that the best arrangement involves the placingv of these weights close to tbe periphery of the sheet as indicated. The stid'ness of the sheet of felt is such that the pressure of these weights is not localized' ing elements. in order to prevent the feltV from becoming water-soaked, a sheet of rubber 18 may be employed upon the face of the felt as indicated at Figure 3, and the back of the felt may be covered vvith a stidpitch 19 which protects the felt and confines the Heribility more or less to the outer portion of the felt sheet.

ln operatingthe devic'e,ra coarse abrasive is first used, as in ordinary wfg operation, followed by finer and finer abrasive, endingup with line grades of emery. This `is followed by a olishing operationin which a runnersimi ar-'to the runner 4l, but

ployed,

Figure 5 illustrates a inodication in which the concave side of the glass sheet 20 is to be ound upon the table 21, the felt sheet 22 eing curved to conform with the Iarranged around the I.

curve of the glassand being supported by the PlalB 23 and PIOVlded With the i Imi 1|, elements 24:, the construction aside the reversal of curvature, being similar to that heretofore described. -v'ljhe weights 25 are eriphery just as in the other construction.

. )Fi e 6 illustrates the use of the rer 26 Without .any grinding elements, this conweights 17 as used in the construction of Figure l.. Throughout the and l polisg operations the ers may be shifted or adjusted from time to e to grinding elements, is em' a curved surface, comprg a spindle, and

a vveigbted' flexible member carried thereby adapted to conform itseM to the curved surfece.. l

2; lin combination, e runner for upon a convex: surface, comprising a spindle,

a deuible member la concave face carried thereby adapted to conform itself to the curved surface, and 'a 41olurality of devices for applying pressure at se arated points upon the bach: ofsaid mem er, tbe' said member sufieient bodyY to prevent the prsure mom Alocalised ,whereby a imiform pressure exerted by the face of the member. Y

3, combination, e runner for use upon a denible member carrie -a curved surface, comprisinga spindle, and

d ere? y adapted to conform itself to the curved surface, and

a plurality of Weights distributed over the rear face ofsaid member.,

4l., In combination, a runner for use upon a curved surface, comi rising a indl face member carried t ereby consistingof a slieet of felt unsupported at its outer por' v tion, adapted to conform itself to tbe curved surface and means for applying pressure ikipon the om portion of said mem- 5. lin combination, a runner for a curved surface comp a spindle, a

'denible face' member carriedY thereby and having 'its outer portion unsupported and comprg a sht of felt adapted to Ycon-A forni itself to the curved surface, a plural# iey of Weights distribud over the rear side o the' felt, and-metal du; cured nponthe front ofY said sheet,

t. lin combination, a runner for acurved surfacecompr a spindle, a flexible face member carrie thereby und ha its outer portion unsupported and' compr up a sheet of felt adapted to confo itse to the curved surface, a plurali of vveiglits distributed over the rear 'side' o thefelt, and metal grindin members' secured upon the front of said slieet, and compr headed members with shanlrs projecting into the sheet.

i". lin combination in and polv ish device,;a er tral vportion comparativel WWP self to the'surface o the lass and a plu# rality of vvei'glitsarrenge upon the rear side of tbe peripberul portion of tbe disco Signed tbis d@ day of Nov., i229.,

n n romtsrou beving its cenand 'its genoeg iio ery-demble' to t it to adapt it-' I 

